The light guide plate is one of the most important components in the backlight module of a display. Light guide plates in the prior art are substantially made from polymethyl methacrylate (PMMA), which has a relatively high coefficient of thermal expansion. In order to facilitate free expansion of the light guide plate, an expansion gap should be provided in advance between the light guide plate and the frame for fixing the light guide plate within a backlight module.
However, on the one hand, an oversized expansion gap provided in advance would affect the optical efficiency of the backlight module, and prevent the frame for fixing the light guide plate from compactly fixing the light guide plate. Therefore, the light guide plate would shake to a certain extent, as a result of which the optical film on the light guide plate would be easily subjected to friction and scratch. On the other hand, an undersized expansion gap provided in advance would lead to insufficient space for accommodating the light guide plate after thermal expansion. As a result, the light guide plate would be compressed at its side edges and arch up, thus inevitably rendering abnormality of display quality.